Varnish on AWS - https is not the only problem, if you have load balancer or auto scaling, you have to use some custom automation, otherwise aws clustering will screw your work...
Hi,
Varnish can handle HTTPS now - they've released their own version of Bumptech's `stud` HTTPS proxy called `hitch`. It's also available as part of Varnish Plus. (I was a contributor to another `stud` fork, and think it's pretty good).
Like davidclarkny2 said, you are looking at spending quite a bit of money to put a "best in class" kind of hosting package together: Varnish, Redis, CDN & fast servers. If you only care about TTFB for SEO reasons, you can probably cheat a little with packages like Nitrogento - the site will still perform slowly when users add to their basket and try and check out - there's no getting around spending money to make the whole site fast - but if web spiders like Google are hitting the cached version of your site they will hopefully register the faster TTFB.